The invention relates to a robotically controlled mobility platform.
Robots are useful in a variety of civilian, military, and law enforcement applications. For instance, a robotically controlled mobility platform inspect or search buildings with structural damage caused by earthquakes, floods, or hurricanes, or inspect buildings or outdoor sites contaminated with radiation, biological agents such as viruses or bacteria, or chemical spills. The platform can carry appropriate sensor systems for its inspection or search tasks. Military applications include operations that are deemed too dangerous for soldiers. For instance, the robot can be used to leverage the effectiveness of a human xe2x80x9cpointman.xe2x80x9d Law enforcement applications include reconnaissance, surveillance, bomb disposal and security patrols.
The mobility approaches that have been used in prior robotic platforms exhibit various shortcomings, many of which are addressed by the present invention.
In one aspect, in general, the invention is an articulated tracked vehicle. The vehicle has a main section which includes a main frame and a forward section. The main frame has two sides and a front end, and includes a pair of parallel main tracks. Each main track includes a flexible continuous belt coupled to a corresponding side of the main frame. The forward section includes an elongated arm having a proximal end and a distal end. The proximal end of the arm is pivotally coupled to the main frame near the forward end of the main frame about a transverse axis that is generally perpendicular to the sides of the main frame.
Alternative embodiments include one or more of the following features:
The arm is sufficiently long to allow the forward section to extend below the main section in at least some degrees of rotation of the arm, and the arm is shorter than the length of the main section.
The center of mass of the main section is located forward of the rearmost point reached by the distal end of the arm in its pivoting about the transverse axis.
The main section is contained within the volume defined by the main tracks and is symmetrical about a horizontal plane, thereby allowing inverted operation of the robot.
The vehicle is dimensioned for climbing a set of stairs. At a first adjusted angle between the main section and the forward section, the forward section rises more than the rise of the bottom-most of the set of stairs. At a second adjusted angle between the main section and the forward section, the length spanned by the combination of the main section and the forward section being greater than the diagonal span of two successive stairs. The center of gravity of the vehicle is located in a position so that the vehicle remains statically stable as it climbs the stairs at the second adjusted angle.
The forward section includes a second arm, also pivotally coupled to the main frame near its forward end. For instance, the arms are coupled to the main frame such that they rotate outside the main tracks. The two arms can be rigidly coupled and rotated together by the articulator motor. The articulator motor provides sufficient torque between the main frame and the arms to raise the rear end of the main section thereby supporting the vehicle on the front section. Continuous rotation of the arms can provide forward locomotion of the vehicle. A harmonic drive can be coupled between the articulator motor and the two arm. The harmonic drive provides a torque to the two arms greater than the torque provided to it by the articulator motor. A clutch can be coupled between the articulator motor and the two arms. The clutch allows rotation of the arms without rotation of the motor if the torque between the arms and the main section exceeds a limit. A pair of flexible forward tracks can be coupled to the two arms.
A pair of drive pulleys for supporting and driving each of the main and forward tracks are included, one on each side of the vehicle. The drive pulleys are coaxial with the transverse axis of rotation of the arms, and are joined so that they rotate together. The vehicle can include a pair of drive motors, one coupled to both the main and forward drive pulleys on a corresponding side of the vehicle.
On each side of the main frame, two compliant pulleys are coupled between one of the main tracks and the main frame, and multiple compliant track supports are coupled between the tracks and the side plates. Each pulley includes a compliant outer rim, a hub, and multiple compliant spoke segments coupled between the rim and the hub.
Multiple compliant longitudinal track supports coupled between the main frame and the continuous belts. Each longitudinal track support has a series of open slots forming a series of rib sections between the upper and lower edges of the support.
The pulleys and main frame are recessed within the volumes defined by the tracks.
Each track includes a flexible continuous belt and a series of compliant cleats attached transversely on the outside of the belt.
The main tracks each include a longitudinal rib coupled to the inside surface of the belt, and each of the pulleys includes a channel around its circumference which accepts the longitudinal rib. The channels are dimensioned larger than the rib thereby allowing debris to be caught between a pulley and a track without dislodging the track from the pulley.
In another aspect, in general, the invention is a method for operating an articulated tracked vehicle having a main tracked chassis and a pivoting forward arm for the vehicle to climb a set of stairs. The method includes pivoting the arm to raise the arm higher than the rise of the bottom-most stair of the set of stairs, then approaching the first stair until the arm contacts the first stair. The method further includes driving the main tracks until the main tracks contacts the first stair, and then pivoting the arm to extend the tracked base of the vehicle. The method then includes driving the main tracks to ascend the set of stairs.
In another aspect, in general, the invention is a method for inverting an articulated tracked vehicle which has a main tracked chassis and a pivoting arm. The method includes supporting the vehicle on the main tracks in a first vertical orientation, supporting the vehicle on the pivoting arm, and then pivoting the arm to raise the main chassis above the supporting surface. Further pivoting of the arm passes the main chassis past a stable point. This results in the vehicle being supported on the main tracks in a second vertical orientation, the second vertical orientation being inverted with respect to the first orientation.
Aspects of the invention include one or more of the following advantages. One advantage is immediate recovery from tumbles in which the vehicle lands on its xe2x80x9cback.xe2x80x9d The vehicle can operate with either side up and therefore does not necessarily require righting. Also, if one vertical orientation is preferable over another, for example, due to placement of sensors, the robot can invert itself to attain a preferred orientation.
Another advantage is impact resistance. Impact resistance allows the robot to operate even after collisions, falls, or tumbles. Furthermore, impact resistance allows deploying the robot in a variety of ways including tossing it from a height, such as from a window or from a helicopter.
The housing of components within the track volume has the advantage that the robot""s components are less likely to be damaged in a fall or tumble. Recessing the side plates of the robot frame within the track volume also reduces the likelihood of impacting the frame in such a tumble or fall.
The robot""s forward center of gravity has the advantage that it aids stair climbing and climbing of steep inclines. Also, a center of gravity within the extent of the forward articulated section allows the robot to perform a self righting operation and to operate in an upright posture by supporting the platform solely on the forward section.
The robot""s articulated body, including continuously rotatable arms, has the advantage that the robot can be driven using a xe2x80x9cpaddlingxe2x80x9d action of the arms. This mode of driving the vehicle is useful, for instance, when the tracks have inadequate traction, for example due to an obstruction supporting the center of the frame.
Compliant idler and drive pulleys provide robustness to debris that may be caught between the tracks and the pulleys. Also, raised segments on the tracks mating with corresponding channels in the outside rims of the idler and drive pulleys reduces the possibility of xe2x80x9cthrowingxe2x80x9d a track. Loose mating of the raised segments and the channels also permits debris being caught between the pulleys and the track without throwing a track or stalling a drive motor.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.